Tick-borne encephalitis (TBE) is a growing public health issue in Poland. Its ecologic determinants and individual risk factors are poorly understood, despite growing number of studies published in Europe in the recent years. In Poland no research projects studying risk factors for TBE have been performed at the national level. Objective: To examine the association of factors related to vector ticks activity and factors related to the probability of tick/human contact with TBE incidence rates at the commune, lowest administrative level of Poland;to develop a predictive model of TBE incidence in Poland;and to study risk factors for TBE using a case-control design. Methods, design: We will perform a preliminary, ecologic study at the commune level of analysis utilizing existing data on TBE from 2,950 cases reported in 1993- 2006 and several ecologic variables obtained for the commune level. These ecologic variables will be: Lyme disease incidence rate, percent of commune area covered by forests, forest types prevalent in a commune, monthly air temperatures, monthly air humidity, monthly rainfall, measures of environmental pollution, and socio-economic status of commune inhabitants. A secondary, case-control study will utilize all cases reported in Poland in a year period. Three control subjects will be selected for each case, frequency matched by age, gender and district of residence. Each control subject will be serologically tested to exclude asymptomatic TBE. The association between exposure and disease will be compared between TBE cases and subjects free of TBE. If the number of asymptomatic TBE cases will be sufficient, an additional comparison between asymptomatic TBE cases and subjects free of TBE will be carried out. The risk factors studied will include visit to area with high risk for TBE, outdoor activities, socio-economic status. This project is aimed to identify population-level and individual-level risk factors related to tick-borne encephalitis, which is a serious problem in Poland. By establishing risk for disease both in areas endemic for the disease and non-endemic, as well as assessment of individual disease risk factors, well targeted public health interventions will be possible using safe and effective prophylaxis and education.